The invention relates to an agitator mill for continuous or discontinuous grinding dispersion, homogenization and emulsifying of microbial, organic and inorganic suspensions, consisting of a grinding container, comprising a stirrer rotating therein and made of a stirrer shaft and a plurality of stirring disks, freely movable grinding elements and a separation device for separating the ground material from the grinding elements at the outlet from the agitator mill.
Known agitator mills of this kind require operation at relatively high rpm and correspondingly high driving power in order to attain good stirring and grinding effects. The high rpm of the stirrer apparatus leads to high relative velocities between the stirring disks and the material subjected to grinding, owing to which the latter can become highly heated, at least locally. Accordingly, such agitator mills are not very suitable for materials that are sensitive to temperature, e.g., microbial cells.
The invention is based on the task of producing an agitator mill which is suitable in particular for sensitive materials and allows their effective treatment with the materials staying only a short time in the agitator mill.
The problem is solved by proceeding according to the invention from an agitator mill of the type described at the outset, so that oblique disks arranged obliquely on the stirrer shaft are provided as stirring disks.
Oblique disks of this kind exhibit such an intensive grinding and/or stirring effect that a high rpm of the stirrer shaft is not required. Consequently, the ground material is subjected to low mechanical stresses. At the same time, the driving power required for driving the stirrer shaft is reduced. Excessive local temperatures are eliminated.
In addition to a flow-velocity component in the peripheral direction, oblique disks produce a flow component in the axial direction; i.e., parallel to the stirrer shaft, which causes a rotation of the entire contents of the agitator mill and brings about an increased number of collisions between the grinding elements and the ground material. Accordingly, one can thus shorten the time for retaining the ground material in the agitator mill.
Oblique disks possess the additional advantage of being suitable in particular for the employment of very small grinding elements; e.g., those of the diameter of 0.1 to 0.7 mm. Such small and light grinding elements are frequently not actuated sufficiently by the disks in the spaces between ordinary, so-called radial or normal disks arranged perpendicularly to the stirrer shaft. With oblique disks one obtains a better actuation of such small grinding elements that are preferably used for the treatment of microbial substances and the like and, besides, are subjected to a lesser wear than larger grinding elements.
While in the case of radial disks situated perpendicularly on the stirrer shaft, relatively stable flow lines are formed, the employment of oblique disks produces an extensive turbulence, so that the relative displacement between grinding elements and particles of ground material is intensified as desired. When oblique disks of invention are employed, a 4 m/s - 18 m/s peripheral velocity of the stirring disks is sufficient for obtaining very good stirring effects.